1. Field of the Invention
The present invention relates to a printing press for doing printing such as offset printing in which inks are applied to printing plates to form ink images, which are then transferred onto printing paper. And especially, the present invention relates to a printing press equipped with a color chart measuring apparatus for reading a color chart printed on printing paper to acquire color chart information.
2. Description of the Background Art
Recently, printing presses which install therein a plate making machine (printing plate recording apparatus) for forming an image on a printing plate on the basis of digital image data, known as a CTP (computer-to-plate) machine, have been developed for commercial use. Such printing presses are called digital printing presses and are suitable for short-time print jobs such as multi-kinds, small-circulation printing, since they can produce printed matter directly from image data. Those digital printing presses have automatized a prepress process for ease of handling by even inexperienced operators, but still further automation of a printing process, such as ink feed control, is desired.
For the control of ink feed, conventional printing presses have generally used a separate type color measurement table for measuring a picked-up printed sample placed thereon. This, however, requires an operator to pick up an appropriate printed sample for color measurements of printed matter.
To solve this problem, printing presses comprising means for capturing an image of printing matter have been proposed. According to this conventional technique, the printing press obtains image data through imaging of printing matter on its impression cylinder and compares this image data with previously-obtained reference image data about reference printing matter for ink feed control. In this conventional technique, an image of printing matter is captured within the printing press, which brings the advantage of avoiding operator involvement which would be required when using the color measurement table.
The above conventional technique, however, has a problem that reading and comparing a whole image of printing matter with a reference image requires handling of a large amount of image data and requires much time for image data processing. In addition, the preparation of a reference image is not suitable for print jobs which require immediacy, such as multi-kinds, small-circulation printing.